It can be regarded as the mascot of the deep sea, with a shining lure over its head and mouth full of sharp teeth. But did you know that only female anglerfish looks like this? The males actually live as parasites on females, and can be ten times smaller than their female counterparts. Before reproduction, these dwarf males swim around with an extremely well-developed nose, in order to smell female pheromones. When the male finds the female he bites into her skin, causing them to fuse and grow together - even linking their blood vessels. This adaptation ensures that whenever a female anglerfish is ready to spawn, her mate is already available. A female may even have more than one male attatched, with the record being 12 males at the same time!

3D model of Oneirodes eschrichtii, the Bulbous dreamer. Oneirodes means dreamlike, or out of a dream, suggesting those who named this fish thought it to be so weird and marvelous that it could only exist in dreams!

Anglerfish are named for their unique predation method. They use a modified fin ray known as the esca, with bioluminescent bacteria which portrudes from its head, shining in the deep sea as a lure which attracts prey. When the prey closes in, the anglerfish is able to snap them up quickly, with their huge mouth. Even if the prey is large - if it can fit in the mouth, it can fit in their stomach. Thanks to its stomachs elasticity, it is able to stretch up to double its size! As such, the anglerfish can take advantage of the few and far between meals available in the deep sea.

An overview of 10 different species of anglerfish - highlighting their different body shapes. (by Masaki Miya et al. Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective. BMC Evolutionary Biology 2010, 10:58 doi:10.1186/1471-2148-10-58)

Their predation mode also explains their weird, bulbous bodies. They are not exactly designed for fast and active swimming, but are rather specialized to sit and wait, and to engulf large prey that get too close. Some are round, like footballs (C in the picture, family: footballfish) while other can be elongated with smaller escae (I in the picture, family: wolftrap seadevils!).

The anglerfish is a staple creature of the deep sea, and a welcome addition to the wonderful, weird and fascinating line-up of twilight zone creatures. Do you want to see and learn about more animals from the deep? Check out our video below!